Stunning theatrical publicity shot featuring Barbara Steele (Helen Rochefort / Mary) wearing a seductive black silk dress resting on her bed.

Black Sunday (Italian: La maschera del demonio, lit. 'The mask of the demon') is a 1960 Italian Gothic horror film directed by Mario Bava in his official directorial debut, and starring Barbara Steele and John Richardson. Loosely based on Nikolai Gogol's short story "Viy", the film takes place in Moldavia and tells the story of a witch who is put to death by her brother, only to return two centuries later to seek revenge upon his descendants.

Having provided cinematography on Hercules (1958) and Hercules Unchained (1959) for the production company Galatea and helping finish two of their other films, Caltiki – The Immortal Monster (1959) and The Giant of Marathon (1959), Bava was permitted by the company's president, Lionello Santi, to make a film for foreign markets; he chose to make a horror film to capitalize on the recent success of Terence Fisher's version of Dracula (1958) for Hammer Film Productions.

After he developed a four-page outline faithfully based on Gogol's story, several other screenwriters, both credited and un-credited, worked on the script. Former Rank Organisation contract players Steele and Richardson were cast as Bava felt that British leads would allow the film to compare favorably to Dracula. Filming took place in the studios of Scalera Film in Rome and on location at Castle Massimo in Arsoli; shooting was complicated by Bava's frequent reworking of the script and Steele's conflicts with the crew.

Black Sunday had limited financial success upon its initial Italian release. It was acquired for distribution in the United States by Samuel Z. Arkoff and James H. Nicholson of American International Pictures (AIP), who oversaw numerous alterations to the film prior to its American release, including the removal of some scenes of violence and sexuality, re-dubbing the dialogue, and replacing Roberto Nicolosi's musical score with one by Les Baxter. The film found greater success upon its American release in 1961 when it became the highest-grossing film to be released by AIP in its first five years of existence. The film was banned for several years in the United Kingdom and did not receive a wide release there until July 1968, when it was released by Border Films as Revenge of the Vampire.

The film received generally negative reviews in Italy but garnered far more positive reviews abroad in France and the United States, where it received favorable notices in Cahiers du Cinéma, New York Daily News, Time, and Variety. Retrospective reception of Black Sunday remains positive: it was placed at number 84 on a Time Out poll of the best horror films, while critic James Marriott praised the film as the "crowning achievement of Italian Gothic horror".

The film is now considered to be a pioneering work that set the standards for Italian horror films due to its juxtaposition of beautiful and horrific elements, with strong depictions of eroticism and graphic violence. These elements would be found in later Italian genres, such as the Spaghetti Western and the Giallo. The film turned Steele into a movie star in Italy, and led to her appearing in several horror film productions throughout the 1960s and 1970s.